mod re500 with sunhans 3w no gain

hi there, i have mod my re500 with a sunhans 3w amp. But the result is very little to no gain in range at all. I have been going through some forum and i saw something called attenuation . Does that help at all? The forum i was reading is someone using a 2w sunhans with a 6dB attenuation. As i am using a 3w sunhans should i be looking for a 6dB attenuation or different one?